Linear motion actuators are generally used for highly precise control of a linear position applicable in display devices, semiconductors, robots, machine tools, and the entire precision instruments industry, and a linear motion mechanism including a linear motion guide, for example, may be used as a linear guide unit that guides linear position control of the linear motion actuator.
When linear motion mechanism systems are configured using the linear motion mechanism, as the weight of the linear motion guide and the weight of a support plate increase, cost for manufacturing the linear motion mechanism system increases, and the speed of the linear motion mechanism system is limited due to an increase in the size (volume) of the linear motion mechanism system.
Such linear motion mechanism systems using the linear motion mechanism are designed and manufactured according to their applied fields and thus are not compatible with other systems, and manufacturing cost thereof increases.
In addition, since the weight of the linear motion mechanism systems is heavy, there is a limitation in applying the linear motion mechanism systems to equipment, and their usage is restrictive.
In these days, linear guide units are disclosed as linear motion mechanisms with better efficiency, the linear guide units including a base member having a function of a prop, a slide member that is slidably installed at the base member, and an actuator that moves the slide member relative to the base member.
A guide portion for guiding slide motion is disposed on both the base member and the slide member, and a linear motion block is installed at the guide portion. The linear motion block includes a ball bearing including a plurality of steel balls that are moved on a caterpillar and embedded in the ball bearing so as to smoothly guide linear motion by minimizing friction that may occur when guiding slide motion.
Such general linear guide units have the following problems.
First, a preload applied to a ball bearing installed at the guide portion disposed on the base member and the slide member cannot be adjusted. That is, the steel balls of the ball bearing are combined with the ball bearing in such a way that the steel balls having the sizes selected according to levels of preloads when the steel balls are initially combined with the ball bearing are inserted in the ball bearing, and the preload of the ball bearing is varied as the ball bearing is worn out when it is being used, and thus the preload of the ball bearing cannot be adjusted. Since, in this way, the preload of the ball bearing cannot be adjusted when the ball bearing is being used, the degree of operation precision that may be lowered when the ball bearing is being used cannot be corrected. Thus, vibration and noise occur, and the life span of the linear guide units is reduced.
Second, the base member and the slide member are formed of heavy metals with high rigidity and high abrasion resistance so as to ensure abrasion resistance so that the range of application of the linear guide units is limited.
Third, steel balls having the same diameter are used in the ball bearing, as illustrated in FIG. 14. Friction between the steel balls occurs when the ball bearing is activated, resulting in accelerating abrasion and occurring noise and vibration.